1) Field of the Invention
The invention herein relates to an improved tape rule blade in which a cross-sectionally concavo-convex tape rule blade having a plurality of gradually varying sections of radii and angles of curvature effectively increases the total length of extension of the tape rule blade and thereby maximizes single operator, fully drawn tape rule measurement span; as such, the tape rule blade structure of the present invention enhances tape rule utility and, furthermore, offers additional industrial practical value.
2) Description of the Prior Art
In a conventional tape rule, referring to FIG. 1, FIG. 2, and FIG. 3, the blade 11 of the said conventional tape rule 10 is concavo-convex in profile to increase its length of extension, the said length of extension refers to the length L that the concavo-convex blade 11 is pulled up out of the tape rule 10 before the blade 11 bends downward due to its own weight, the length of extension L thus indicating how much downward force the blade 11 is capable of withstanding before flexure; as illustrated, the cross-sectional face of the conventional blade 11 is approximately one inch (25 mm) in widthxe2x80x94which is typical for a standard blade 11, with the blade 11 having a curvature of R14 at the center and, furthermore, an elevation angle of 34 degrees at its two sides, which in industrial terms is noted as R14 34 degrees; the length of extension of the said conventional blade 11, as indicated by the L of the drawn out tape rule 10 blade 11 is approximately seven feet, which limits the total extended measurement length by a single operator. In view of the shortcomings awaiting solution of the conventional product, the inventor of the invention herein originated several innovative ideas through extensive research based on specialized knowledge as well as design experience accumulated while engaged in the related fields which culminated in the successful designing of the improved tape rule blade of the invention herein.
The objective of the invention herein is to provide an improved tape rule blade in which a cross-sectionally concavo-convex tape rule blade having a plurality of sectional variations and, furthermore, the radii of curvature at the rear section of the tape rule blade are smaller than the radii of curvature at the forward section of the tape rule blade, while the angle of elevation along the two sides at the rear section of the tape rule blade are larger than the angle of elevation along the two sides at the forward section of the tape rule blade, thereby increasing the total length of extension of the tape rule blade, maximizing single operator, fully drawn tape rule measurement span and enhancing tape rule utility.
To enable a further understanding by the examination committee of how the said aims are achieved as well as the advantages, other objectives, and functions of the invention herein, the brief description of the drawings below are followed by a detailed description of the preferred embodiment of the present invention.